Load .dll texture plugin
First off, the forum you linked to was talking about version 2.3x. (If you look at the post's dates it was from 2004!) We are using 2.77 now, a lot has changed.

Back then, and up till 2.4x you could use texture plugins. There is no way to use a .dll texture in blender now.
There is OSL scripting in cycles, so you could recode one if you really want to.

Now a days, textures are used a little differently. See my answer to
How are texture maps imported into Blender? for how to import image textures in cycles, and blender internal.